The purposes of the proposed research are: (1) to evaluate the clinical use of vasoactive intestinal peptide cross-reactive material VIP-CRM as a biochemical marker in acute myelocytic leukemia (AML) and chronic myelocytic leukemia (CML); (2) to confirm the structural identity of VIP-CRM and (3) to study the role of VIP or VIP-CRM in the function of human lymphocytes. Initial studies in peripheral blood are very promising and ongoing studies in bone marrow show the same specificity. The evidence to date indicates that VIP-CRM together with adenosine deaminase and terminal deoxynucleotidyl transferase measurements on bone marrow buffy coat cells may be an effective means of predicting the onset of blastic crisis in CML and further characterizing the blastic transformation as myeloid or lymphoid. VIP receptors have been characterized on human T lymphocytes and in a transformed T lymphocyte cell line. In both cases, VIP receptor binding activates adenylate cyclase. The lymphoblasts are more sensitive to VIP stimulation than are mature T cells, suggesting that VIP may play a role in the proliferation or differentiation of human lymphocytes.